Investigation of the change in the refractive index of the active medium of a laser by the optical delay method utilizing emitted radiation

An optical delay method is proposed for investigation of the change in the refractive index of the active medium of a laser at the wavelength of its stimulated emission. Criteria of the validity of this method are obtained and an analysis is made of the errors in the measurement of Δn. A specific optical delay system is described and tested in an experimental determination of the distribution of Δn in an iodine laser pumped by an open discharge. The results of simultaneous measurements of Δn in the light of a ruby laser are also reported. The distributions of Δn at the emission wavelength of the iodine laser (1.315 μ) and at the ruby laser wavelength (0.6943 μ) are identical. The experimental results are used in an estimate of the characteristics of the wave front of the radiation emitted from the iodine laser.